add selector

selector/filter.go

@@ -0,0 +1,87 @@
+package selector
+
+import (
+	"time"
+
+	mdutil "github.com/go-gost/core/metadata/util"
+	"github.com/go-gost/core/selector"
+)
+
+type failFilter[T selector.Selectable] struct {
+	maxFails    int
+	failTimeout time.Duration
+}
+
+// FailFilter filters the dead objects.
+// An object is marked as dead if its failed count is greater than MaxFails.
+func FailFilter[T selector.Selectable](maxFails int, timeout time.Duration) selector.Filter[T] {
+	return &failFilter[T]{
+		maxFails:    maxFails,
+		failTimeout: timeout,
+	}
+}
+
+// Filter filters dead objects.
+func (f *failFilter[T]) Filter(vs ...T) []T {
+	if len(vs) <= 1 {
+		return vs
+	}
+	var l []T
+	for _, v := range vs {
+		maxFails := f.maxFails
+		failTimeout := f.failTimeout
+		if md := v.Metadata(); md != nil {
+			if md.IsExists(labelMaxFails) {
+				maxFails = mdutil.GetInt(md, labelMaxFails)
+			}
+			if md.IsExists(labelFailTimeout) {
+				failTimeout = mdutil.GetDuration(md, labelFailTimeout)
+			}
+		}
+		if maxFails <= 0 {
+			maxFails = 1
+		}
+		if failTimeout <= 0 {
+			failTimeout = DefaultFailTimeout
+		}
+
+		if marker := v.Marker(); marker != nil {
+			if marker.Count() < int64(maxFails) ||
+				time.Since(marker.Time()) >= failTimeout {
+				l = append(l, v)
+			}
+		} else {
+			l = append(l, v)
+		}
+	}
+	return l
+}
+
+type backupFilter[T selector.Selectable] struct{}
+
+// BackupFilter filters the backup objects.
+// An object is marked as backup if its metadata has backup flag.
+func BackupFilter[T selector.Selectable]() selector.Filter[T] {
+	return &backupFilter[T]{}
+}
+
+// Filter filters backup objects.
+func (f *backupFilter[T]) Filter(vs ...T) []T {
+	if len(vs) <= 1 {
+		return vs
+	}
+
+	var l, backups []T
+	for _, v := range vs {
+		if mdutil.GetBool(v.Metadata(), labelBackup) {
+			backups = append(backups, v)
+		} else {
+			l = append(l, v)
+		}
+	}
+
+	if len(l) == 0 {
+		return backups
+	}
+	return l
+}

selector/selector.go

@@ -0,0 +1,54 @@
+package selector
+
+import (
+	"time"
+
+	"github.com/go-gost/core/chain"
+	"github.com/go-gost/core/selector"
+)
+
+// default options for FailFilter
+const (
+	DefaultMaxFails    = 1
+	DefaultFailTimeout = 10 * time.Second
+)
+
+const (
+	labelWeight      = "weight"
+	labelBackup      = "backup"
+	labelMaxFails    = "maxFails"
+	labelFailTimeout = "failTimeout"
+)
+
+var (
+	DefaultNodeSelector = NewSelector(
+		RoundRobinStrategy[*chain.Node](),
+		// FailFilter[*Node](1, DefaultFailTimeout),
+	)
+	DefaultChainSelector = NewSelector(
+		RoundRobinStrategy[chain.SelectableChainer](),
+		// FailFilter[SelectableChainer](1, DefaultFailTimeout),
+	)
+)
+
+type defaultSelector[T selector.Selectable] struct {
+	strategy selector.Strategy[T]
+	filters  []selector.Filter[T]
+}
+
+func NewSelector[T selector.Selectable](strategy selector.Strategy[T], filters ...selector.Filter[T]) selector.Selector[T] {
+	return &defaultSelector[T]{
+		filters:  filters,
+		strategy: strategy,
+	}
+}
+
+func (s *defaultSelector[T]) Select(vs ...T) (v T) {
+	for _, filter := range s.filters {
+		vs = filter.Filter(vs...)
+	}
+	if len(vs) == 0 {
+		return
+	}
+	return s.strategy.Apply(vs...)
+}

selector/strategy.go

@@ -0,0 +1,72 @@
+package selector
+
+import (
+	"math/rand"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/go-gost/core/selector"
+)
+
+type roundRobinStrategy[T selector.Selectable] struct {
+	counter uint64
+}
+
+// RoundRobinStrategy is a strategy for node selector.
+// The node will be selected by round-robin algorithm.
+func RoundRobinStrategy[T selector.Selectable]() selector.Strategy[T] {
+	return &roundRobinStrategy[T]{}
+}
+
+func (s *roundRobinStrategy[T]) Apply(vs ...T) (v T) {
+	if len(vs) == 0 {
+		return
+	}
+
+	n := atomic.AddUint64(&s.counter, 1) - 1
+	return vs[int(n%uint64(len(vs)))]
+}
+
+type randomStrategy[T selector.Selectable] struct {
+	rand *rand.Rand
+	mux  sync.Mutex
+}
+
+// RandomStrategy is a strategy for node selector.
+// The node will be selected randomly.
+func RandomStrategy[T selector.Selectable]() selector.Strategy[T] {
+	return &randomStrategy[T]{
+		rand: rand.New(rand.NewSource(time.Now().UnixNano())),
+	}
+}
+
+func (s *randomStrategy[T]) Apply(vs ...T) (v T) {
+	if len(vs) == 0 {
+		return
+	}
+
+	s.mux.Lock()
+	defer s.mux.Unlock()
+
+	r := s.rand.Int()
+
+	return vs[r%len(vs)]
+}
+
+type fifoStrategy[T selector.Selectable] struct{}
+
+// FIFOStrategy is a strategy for node selector.
+// The node will be selected from first to last,
+// and will stick to the selected node until it is failed.
+func FIFOStrategy[T selector.Selectable]() selector.Strategy[T] {
+	return &fifoStrategy[T]{}
+}
+
+// Apply applies the fifo strategy for the nodes.
+func (s *fifoStrategy[T]) Apply(vs ...T) (v T) {
+	if len(vs) == 0 {
+		return
+	}
+	return vs[0]
+}